The program goal is to train pre-doctoral and postdoctoral biostatisticians in statistical theory and methods as applied to HIV/AID. This aim is addressed by an integrated collaboration between biostatisticians and HIV/AIDS to provide: supervision by biostatisticians with extensive experience in the development of statistical methodology; interaction with researchers with extensive experience in HIV/AIDS; practical experience in the applications of statistical methodology to problems in AIDS clinical trials and observatory studies by participating in consulting projects and attending colloquia; mentoring of trainees to assist in developing independent academic careers. Training: This training program is a collaboration between the Departments of Biostatistics and Computational Biology (DBCB), the Infectious Diseases Division in the Department of Medicine, Department of Microbiology & Immunology, and the Department of Community and Preventive Medicine. The DBCB offers a Ph.D. degree in Statistics with an option in Biostatistics. The Department, created to foster biostatistical research and collaboration with researchers in the Medical Center, provides the administrative leadership and the critical link with the HIV/AIDS investigators. Trainees will be matched with a biostatistician as primary preceptor and an AIDS investigator as a secondary cosponsor. The Training Grant Committee will review the progress of the trainees and the program. Trainees: Predoctoral trainees will have completed a baccalaureate degree with a major in mathematics, statistics, or a science major with a strong minor in mathematics or statistics. Selection is based on academic record, GRE scores, and recommendations. Predoctoral trainees must fulfill the standard requirements for the Ph. D. degree in statistics plus additional courses in biostatistics, epidemiology and HIV prevention. Two predoctoral four-year awards will be granted. Postdoctoral trainees must have completed a Ph. D. in statistics, mathematics or a related discipline. Each postdoctoral trainee will enroll in appropriate courses, attend seminars, and work with faculty mentors on biostatistics research and specific AIDS related projects. Three postdoctoral traineeships are awarded to establish an alternating two-year program.